My son was born with Spina Bifida and had surgery at 9mo to close the spinal canal, everything was fine with his legs, normal growth, size, strength etc. untill 3 yr ago when his left leg started to weakened, numb and atrophy. After back surgery to decompress and detether cord, he regained feeling, strength, and his leg even grew and is now equial length to right leg, but his calf muscle is still continuing to atrophy. Can something else other than SB be the cause of this???